This invention relates to a control device for a periodically oscillating member, the amplitudes of which in opposite directions are different from each other when a predetermined balanced condition is not maintained.
Frequently, it is necessary to adapt the drive of an oscillating member to the average speed of another drive unit. For example, if the input of material into a machine is continuous or discontinuous and the oscillating member serves to process the material in the machine or to discharge the material from the machine, it is frequently necessary to maintain the speed of the periodic oscillation movement such that it corresponds to the average speed of the input of material so that the amount of material discharged from the machine consistently corresponds on the average to the amount of material supplied to the machine.
If the amplitude of the oscillating member in one direction surpasses and in the other direction falls short of the predetermined average speed of the drive unit, the oscillation range of the oscillating member is caused to migrate due to the incorrect drive speed. The deviation from the correct drive speed is cumulative so that the oscillating range is altered. If limit switches are positioned at the opposite predetermined limits of the oscillation range, a signal will be emitted by one of the limit switches each time the oscillating member exceeds the position of the one limit switch which could serve to adjust the speed of the drive unit. However, the limit switch would also emit a signal when the oscillating member stopped and did not exceed the position of the limit switch causing the speed of the drive unit to be changed even though such change was not warranted. If, when simple limit switches are used, a pulse clock is transmitted via a closed limit switch so that adjusting pulses are supplied to the drive unit, too many adjusting pulses will be transmitted over too long a period of time with each amplitude so that the control circuit tends to cause overmodulation which is a disadvantage.
It is an object of the present invention to provide a simple and economically constructed control device for use with a periodically oscillating member which does not have the disadvantages of overcontrol and undercontrol oscillations.